Blast doors are required for blast-hardened structures such as military command centers, personnel shelters, explosives research control rooms, petroleum refinery control rooms, or ordnance assembly facilities or other applications in which doors may be exposed to explosive blasts. The doors allow entry into the protected space without breaching protection.
Blast doors must be able to withstand the initial blast overpressure, the force of the rebounding doorplate, and the explosion-induced ground shock. They should be fireproofed in accordance with National Fire Protection Association standards, which require "panic hardware" for opening the door and an automatic closer. It is also desirable that low force be required to operate the latch mechanism and to open and close the door, and that the latch mechanism be extremely reliable for many years.
Panic hardware for doors of public buildings are known. Symon, U.S. Pat. No. 4,488,378; Miller, U.S. Pat. No. 4,295,673; Ellingsen, U.S. Pat. No. 3,940,886; Godec, U.S. Pat. No. 4,167,280; Horgan U.S. Pat. No. 4,382,620. However, this panic hardware is not adapted for proper operation during and after an explosion. The overall scheme of a horizontal panic bar, a vertical travel bar actuator, and upper and lower latching means are conventional. Welch, U.S. Pat. No. 3,563,585. However, novel adaptations of this overall design were made here to provide blast door capability.
Independently operable inner handle releasing mechanisms are known. Eatinger, U.S. Pat. No. 2,948,561; Butterfield, U.S. Pat. No. 4,072,331. However, these references do not teach adaptation of such mechanisms for use in a blast-resistant latching system.
Biasing latch mechanisms toward a closed position is known. Lindquist, U.S. Pat. No. 4,429,909; Vodra, U.S. Pat. No. 4,545,606.
Gravity-actuated lock mechanisms are also known. Offen, U.S. Pat. No. 2,631,439; Smith, U.S. Pat. No. 3,642,314; Nagy, U.S. Pat. No. 3,778,933. However, no blast door having a latching system which is gravitationally biased toward the latched position by the weight of a latch activating-travel bar means is known.
Inertial lock mechanisms for car door locks are known. Leslie, U.S. Pat. No. 2,864,641; Lemaire, U.S. Pat. No. 3,066,964; Register, U.S. Pat. No. 3,990,531; Slavin, U.S. Pat. No. 4,422,522; Breitschwerdt, U.S. Pat. No. 3,719,248; Nozumu, U.S. Pat. No. 3,799,596; Davis, U.S. Pat. No. 4,007,557. However, the present invention is directed to a pivoting inertial stop which prevents a vertically moving travel bar means from causing the withdrawal of a latch bolt, said stop interposing itself only in response to blast forces.
"Handed" locks are known. Maurits, U.S. Pat. No. 3,499,789. However, the present invention is directed to a latching system in which all the essential elements may be used on either a left- or a right-swinging door.